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llvm-6502/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
Ulrich Weigand 7a34599db0 [PowerPC] Revert r185476 and fix up TLS variant kinds 
In the commit message to r185476 I wrote:

>The PowerPC-specific modifiers VK_PPC_TLSGD and VK_PPC_TLSLD
>correspond exactly to the generic modifiers VK_TLSGD and VK_TLSLD.
>This causes some confusion with the asm parser, since VK_PPC_TLSGD
>is output as @tlsgd, which is then read back in as VK_TLSGD.
>
>To avoid this confusion, this patch removes the PowerPC-specific
>modifiers and uses the generic modifiers throughout.  (The only
>drawback is that the generic modifiers are printed in upper case
>while the usual convention on PowerPC is to use lower-case modifiers.
>But this is just a cosmetic issue.)

This was unfortunately incorrect, there is is fact another,
serious drawback to using the default VK_TLSLD/VK_TLSGD
variant kinds: using these causes ELFObjectWriter::RelocNeedsGOT
to return true, which in turn causes the ELFObjectWriter to emit
an undefined reference to _GLOBAL_OFFSET_TABLE_.

This is a problem on powerpc64, because it uses the TOC instead
of the GOT, and the linker does not provide _GLOBAL_OFFSET_TABLE_,
so the symbol remains undefined.  This means shared libraries
using TLS built with the integrated assembler are currently
broken.

While the whole RelocNeedsGOT / _GLOBAL_OFFSET_TABLE_ situation
probably ought to be properly fixed at some point, for now I'm
simply reverting the r185476 commit.  Now this in turn exposes
the breakage of handling @tlsgd/@tlsld in the asm parser that
this check-in was originally intended to fix.

To avoid this regression, I'm also adding a different fix for
this problem: while common code now parses @tlsgd as VK_TLSGD,
a special hack in the asm parser translates this code to the
platform-specific VK_PPC_TLSGD that the back-end now expects.
While this is not really pretty, it's self-contained and
shouldn't hurt anything else for now.  One the underlying
problem is fixed, this hack can be reverted again.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185945 91177308-0d34-0410-b5e6-96231b3b80d8
2013-07-09 16:41:09 +00:00

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//===-- PPCELFObjectWriter.cpp - PPC ELF Writer ---------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/PPCMCTargetDesc.h"
#include "MCTargetDesc/PPCFixupKinds.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
namespace {
class PPCELFObjectWriter : public MCELFObjectTargetWriter {
public:
PPCELFObjectWriter(bool Is64Bit, uint8_t OSABI);
virtual ~PPCELFObjectWriter();
protected:
virtual unsigned getRelocTypeInner(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const;
virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
bool IsPCRel, bool IsRelocWithSymbol,
int64_t Addend) const;
virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
const MCValue &Target,
const MCFragment &F,
const MCFixup &Fixup,
bool IsPCRel) const;
virtual const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const;
};
}
PPCELFObjectWriter::PPCELFObjectWriter(bool Is64Bit, uint8_t OSABI)
: MCELFObjectTargetWriter(Is64Bit, OSABI,
Is64Bit ? ELF::EM_PPC64 : ELF::EM_PPC,
/*HasRelocationAddend*/ true) {}
PPCELFObjectWriter::~PPCELFObjectWriter() {
}
unsigned PPCELFObjectWriter::getRelocTypeInner(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const
{
MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
// determine the type of the relocation
unsigned Type;
if (IsPCRel) {
switch ((unsigned)Fixup.getKind()) {
default:
llvm_unreachable("Unimplemented");
case PPC::fixup_ppc_br24:
case PPC::fixup_ppc_br24abs:
Type = ELF::R_PPC_REL24;
break;
case PPC::fixup_ppc_brcond14:
case PPC::fixup_ppc_brcond14abs:
Type = ELF::R_PPC_REL14;
break;
case PPC::fixup_ppc_half16:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC_REL16;
break;
case MCSymbolRefExpr::VK_PPC_LO:
Type = ELF::R_PPC_REL16_LO;
break;
case MCSymbolRefExpr::VK_PPC_HI:
Type = ELF::R_PPC_REL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_HA:
Type = ELF::R_PPC_REL16_HA;
break;
}
break;
case FK_Data_4:
case FK_PCRel_4:
Type = ELF::R_PPC_REL32;
break;
case FK_Data_8:
case FK_PCRel_8:
Type = ELF::R_PPC64_REL64;
break;
}
} else {
switch ((unsigned)Fixup.getKind()) {
default: llvm_unreachable("invalid fixup kind!");
case PPC::fixup_ppc_br24abs:
Type = ELF::R_PPC_ADDR24;
break;
case PPC::fixup_ppc_brcond14abs:
Type = ELF::R_PPC_ADDR14; // XXX: or BRNTAKEN?_
break;
case PPC::fixup_ppc_half16:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC_ADDR16;
break;
case MCSymbolRefExpr::VK_PPC_LO:
Type = ELF::R_PPC_ADDR16_LO;
break;
case MCSymbolRefExpr::VK_PPC_HI:
Type = ELF::R_PPC_ADDR16_HI;
break;
case MCSymbolRefExpr::VK_PPC_HA:
Type = ELF::R_PPC_ADDR16_HA;
break;
case MCSymbolRefExpr::VK_PPC_HIGHER:
Type = ELF::R_PPC64_ADDR16_HIGHER;
break;
case MCSymbolRefExpr::VK_PPC_HIGHERA:
Type = ELF::R_PPC64_ADDR16_HIGHERA;
break;
case MCSymbolRefExpr::VK_PPC_HIGHEST:
Type = ELF::R_PPC64_ADDR16_HIGHEST;
break;
case MCSymbolRefExpr::VK_PPC_HIGHESTA:
Type = ELF::R_PPC64_ADDR16_HIGHESTA;
break;
case MCSymbolRefExpr::VK_GOT:
Type = ELF::R_PPC_GOT16;
break;
case MCSymbolRefExpr::VK_PPC_GOT_LO:
Type = ELF::R_PPC_GOT16_LO;
break;
case MCSymbolRefExpr::VK_PPC_GOT_HI:
Type = ELF::R_PPC_GOT16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_HA:
Type = ELF::R_PPC_GOT16_HA;
break;
case MCSymbolRefExpr::VK_PPC_TOC:
Type = ELF::R_PPC64_TOC16;
break;
case MCSymbolRefExpr::VK_PPC_TOC_LO:
Type = ELF::R_PPC64_TOC16_LO;
break;
case MCSymbolRefExpr::VK_PPC_TOC_HI:
Type = ELF::R_PPC64_TOC16_HI;
break;
case MCSymbolRefExpr::VK_PPC_TOC_HA:
Type = ELF::R_PPC64_TOC16_HA;
break;
case MCSymbolRefExpr::VK_PPC_TPREL:
Type = ELF::R_PPC_TPREL16;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_LO:
Type = ELF::R_PPC_TPREL16_LO;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HI:
Type = ELF::R_PPC_TPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HA:
Type = ELF::R_PPC_TPREL16_HA;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
Type = ELF::R_PPC64_TPREL16_HIGHER;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
Type = ELF::R_PPC64_TPREL16_HIGHERA;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
Type = ELF::R_PPC64_TPREL16_HIGHEST;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
Type = ELF::R_PPC64_TPREL16_HIGHESTA;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL:
Type = ELF::R_PPC64_DTPREL16;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
Type = ELF::R_PPC64_DTPREL16_LO;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
Type = ELF::R_PPC64_DTPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
Type = ELF::R_PPC64_DTPREL16_HA;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
Type = ELF::R_PPC64_DTPREL16_HIGHER;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
Type = ELF::R_PPC64_DTPREL16_HIGHERA;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
Type = ELF::R_PPC64_DTPREL16_HIGHEST;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
Type = ELF::R_PPC64_DTPREL16_HIGHESTA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
Type = ELF::R_PPC64_GOT_TLSGD16;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
Type = ELF::R_PPC64_GOT_TLSGD16_LO;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
Type = ELF::R_PPC64_GOT_TLSGD16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
Type = ELF::R_PPC64_GOT_TLSGD16_HA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
Type = ELF::R_PPC64_GOT_TLSLD16;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
Type = ELF::R_PPC64_GOT_TLSLD16_LO;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
Type = ELF::R_PPC64_GOT_TLSLD16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
Type = ELF::R_PPC64_GOT_TLSLD16_HA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
/* We don't have R_PPC64_GOT_TPREL16, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_TPREL16_DS. */
Type = ELF::R_PPC64_GOT_TPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
/* We don't have R_PPC64_GOT_TPREL16_LO, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_TPREL16_LO_DS. */
Type = ELF::R_PPC64_GOT_TPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
Type = ELF::R_PPC64_GOT_TPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
/* We don't have R_PPC64_GOT_DTPREL16, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_DTPREL16_DS. */
Type = ELF::R_PPC64_GOT_DTPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
/* We don't have R_PPC64_GOT_DTPREL16_LO, but since GOT offsets
are always 4-aligned, we can use R_PPC64_GOT_DTPREL16_LO_DS. */
Type = ELF::R_PPC64_GOT_DTPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
Type = ELF::R_PPC64_GOT_TPREL16_HA;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
Type = ELF::R_PPC64_GOT_DTPREL16_HI;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
Type = ELF::R_PPC64_GOT_DTPREL16_HA;
break;
}
break;
case PPC::fixup_ppc_half16ds:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC64_ADDR16_DS;
break;
case MCSymbolRefExpr::VK_PPC_LO:
Type = ELF::R_PPC64_ADDR16_LO_DS;
break;
case MCSymbolRefExpr::VK_GOT:
Type = ELF::R_PPC64_GOT16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_LO:
Type = ELF::R_PPC64_GOT16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_TOC:
Type = ELF::R_PPC64_TOC16_DS;
break;
case MCSymbolRefExpr::VK_PPC_TOC_LO:
Type = ELF::R_PPC64_TOC16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_TPREL:
Type = ELF::R_PPC64_TPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_TPREL_LO:
Type = ELF::R_PPC64_TPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL:
Type = ELF::R_PPC64_DTPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
Type = ELF::R_PPC64_DTPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
Type = ELF::R_PPC64_GOT_TPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
Type = ELF::R_PPC64_GOT_TPREL16_LO_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
Type = ELF::R_PPC64_GOT_DTPREL16_DS;
break;
case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
Type = ELF::R_PPC64_GOT_DTPREL16_LO_DS;
break;
}
break;
case PPC::fixup_ppc_nofixup:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_PPC_TLSGD:
Type = ELF::R_PPC64_TLSGD;
break;
case MCSymbolRefExpr::VK_PPC_TLSLD:
Type = ELF::R_PPC64_TLSLD;
break;
case MCSymbolRefExpr::VK_PPC_TLS:
Type = ELF::R_PPC64_TLS;
break;
}
break;
case FK_Data_8:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_PPC_TOCBASE:
Type = ELF::R_PPC64_TOC;
break;
case MCSymbolRefExpr::VK_None:
Type = ELF::R_PPC64_ADDR64;
break;
case MCSymbolRefExpr::VK_PPC_DTPMOD:
Type = ELF::R_PPC64_DTPMOD64;
break;
case MCSymbolRefExpr::VK_PPC_TPREL:
Type = ELF::R_PPC64_TPREL64;
break;
case MCSymbolRefExpr::VK_PPC_DTPREL:
Type = ELF::R_PPC64_DTPREL64;
break;
}
break;
case FK_Data_4:
Type = ELF::R_PPC_ADDR32;
break;
case FK_Data_2:
Type = ELF::R_PPC_ADDR16;
break;
}
}
return Type;
}
unsigned PPCELFObjectWriter::GetRelocType(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel,
bool IsRelocWithSymbol,
int64_t Addend) const {
return getRelocTypeInner(Target, Fixup, IsPCRel);
}
const MCSymbol *PPCELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
const MCValue &Target,
const MCFragment &F,
const MCFixup &Fixup,
bool IsPCRel) const {
assert(Target.getSymA() && "SymA cannot be 0");
MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
bool EmitThisSym;
switch (Modifier) {
// GOT references always need a relocation, even if the
// target symbol is local.
case MCSymbolRefExpr::VK_GOT:
case MCSymbolRefExpr::VK_PPC_GOT_LO:
case MCSymbolRefExpr::VK_PPC_GOT_HI:
case MCSymbolRefExpr::VK_PPC_GOT_HA:
EmitThisSym = true;
break;
default:
EmitThisSym = false;
break;
}
if (EmitThisSym)
return &Target.getSymA()->getSymbol().AliasedSymbol();
return NULL;
}
const MCSymbol *PPCELFObjectWriter::undefinedExplicitRelSym(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const {
assert(Target.getSymA() && "SymA cannot be 0");
const MCSymbol &Symbol = Target.getSymA()->getSymbol().AliasedSymbol();
unsigned RelocType = getRelocTypeInner(Target, Fixup, IsPCRel);
// The .odp creation emits a relocation against the symbol ".TOC." which
// create a R_PPC64_TOC relocation. However the relocation symbol name
// in final object creation should be NULL, since the symbol does not
// really exist, it is just the reference to TOC base for the current
// object file.
bool EmitThisSym = RelocType != ELF::R_PPC64_TOC;
if (EmitThisSym && !Symbol.isTemporary())
return &Symbol;
return NULL;
}
MCObjectWriter *llvm::createPPCELFObjectWriter(raw_ostream &OS,
bool Is64Bit,
uint8_t OSABI) {
MCELFObjectTargetWriter *MOTW = new PPCELFObjectWriter(Is64Bit, OSABI);
return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/false);
}
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